JP2007048944A - Solar cell back sealing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell back sealing sheet composed of a polyester film such as polyethylene terephthalate superior in electric insulation in place of aluminum foil having the problem that it is short-circuited by touching it, and a technology for providing the solar cell back sealing sheet which does not deteriorate adhesion to an ethylene-vinyl acetate copolymer being a filler. <P>SOLUTION: The solar cell back sealing sheet has an easy-to-adhere coat layer on the surface adhered to a filler forming a solar cell module, and the easy-to-adhere coat layer has a cross-linked structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell back surface sealing sheet, and more specifically, a solar cell back surface capable of improving adhesion with a filler constituting a solar cell module and storage stability over time of the adhesion. The present invention relates to a sealing sheet.

  In recent years, various efforts have been made to suppress carbon dioxide emissions while interest from various countries both inside and outside Japan has increased. Increasing fossil fuel consumption leads to an increase in atmospheric carbon dioxide, and the greenhouse effect raises the Earth's temperature, significantly affecting the global environment. Various studies have been carried out to solve this global problem, and in particular, solar power generation is highly expected in terms of cleanliness and non-pollution. Solar cells constitute the heart of a photovoltaic power generation system that directly converts sunlight energy into electricity, and are made of single crystal, polycrystalline, or amorphous silicon semiconductors. As a structure thereof, a single solar cell element (cell) is not used as it is, and generally several to several tens of solar cell elements are wired in series and in parallel, for a long time (about 20 years). In order to protect the cell, various parsing is performed and unitized. The unit incorporated in this package is called a solar cell module, and the surface that is generally exposed to sunlight is covered with a glass surface, and the gap is filled with a filler made of a thermoplastic (especially ethylene-vinyl acetate copolymer), The back surface is protected by a sealing sheet (FIG. 1).

  Since these solar cell modules are mainly used outdoors, sufficient durability and weather resistance are required in the configuration and material structure thereof. In particular, the back surface sealing sheet is required to have a weather resistance and a low water vapor transmission rate (excellent moisture barrier property). This is because if the filler is peeled off or discolored due to the permeation of moisture or the wiring is corroded, the module output itself may be affected.

  Conventionally, as a solar cell back surface sealing sheet, such as polyvinyl fluoride and polyvinylidene fluoride (including a copolymer with ethylene), such as weather resistance, flame retardancy, and a solar cell module filler are often used. A "fluorine resin" having good adhesiveness with an ethylene-vinyl acetate copolymer has been used (Patent Documents 1, 2, etc.). However, the fluorine-based resin has low mechanical strength and high cost, and further has problems such as generation of a halogen-based toxic gas when the solar cell module is incinerated. In addition, in order to improve the moisture barrier property, a high gas barrier substrate such as an aluminum substrate was provided between the films made of these fluororesins. However, using aluminum foil presents a problem in terms of disposal. Is being viewed. Furthermore, since the fluororesin has a low mechanical strength as described above, when the solar battery cells are filled with the filler, the back surface sealing sheet is destroyed by the protrusions and comes into contact with the aluminum substrate. The problem of short-circuiting is mentioned.

  In order to solve these problems, a solar cell back surface sealing sheet using a polyester film such as polyethylene terephthalate having excellent electrical insulation instead of an aluminum foil has been developed. However, the disadvantages of using a polyester film include weather resistance, and in order to improve them, a system containing a UV absorber (such as Patent Document 3) and the amount of cyclic oligomer in the polyester are defined (Patent Document 4, 5), and the like, there are many disclosures that define the molecular weight of polyester (Patent Document 6 and the like). However, a disadvantage of using a polyester film is adhesion to a filler (ethylene-vinyl acetate copolymer) constituting the solar cell module.

  As described above, the solar cell needs to maintain its performance for about 20 years, and an accelerated test at high temperature and high humidity (85 ° C.-85% relative humidity) is performed to evaluate its durability. At this time, the sheet for sealing the back surface of a solar cell made of a polyester film and the ethylene-vinyl acetate copolymer as a filler are bonded by wetting using the affinity between polar groups and intermolecular interactions such as hydrogen bonding. However, since the adhesion immediately after manufacturing the solar cell module is excellent, it has been confirmed that the adhesion is remarkably reduced in the above environment. In order to improve these, it can be seen that corona treatment is performed on the surface to be bonded to the filler of the solar cell back surface protection sheet (Patent Document 7). However, even if corona treatment is performed, the above problems have not been improved. Is the situation.

  In order to improve this problem, it can be seen that an adhesive film having good thermal adhesion to a filler such as an ethylene-vinyl acetate copolymer is further laminated on a solar cell back surface sealing sheet. (Patent Document 8, etc.), in providing an adhesive film that is thermally bonded to the filler ethylene-vinyl acetate copolymer, the extrusion lamination method is inferior in adhesion to the polyester film as the base material, and is dry. The laminating method has problems such as remarkably lower processability due to blocking of the adhesive film itself. Therefore, it can be seen that an ethylene-vinyl acetate copolymer itself, which is a filler for a solar cell module, is used as the adhesive film (Patent Document 9, etc.), but an ethylene-vinyl acetate copolymer for a solar cell module filler is also disclosed. The polymer is composed of a resin composition containing various additives such as a peroxide and a crosslinking agent, which will be described later, and its processability itself is difficult. At the same time, the filler used in a normal solar cell module is a solar cell. The manufacturer has a strong choice, so it has a problem that it is restricted in the areas that can be marketed.

  From the above points, a sheet for solar cell backside sealing having good adhesion to the ethylene-vinyl acetate copolymer as a filler is desired, but at present it has not yet been solved. is there.

Patent documents are as follows.
JP-T 8-500214 Special Table 2002-520820 JP 2001-1111073 A Japanese Patent Laid-Open No. 2002-100788 JP 2002-134771 A JP 2002-26354 A JP 2000-243999 A Japanese Patent Laid-Open No. 10-25357 JP 2000-174296 A

The subject of this invention considers said situation, and provides the solar cell back surface sealing sheet | seat which can give favorable adhesiveness with the filler which comprises a solar cell module.

The present invention has been devised in order to overcome the above-mentioned problems,
The invention described in claim 1 is a solar cell back surface sealing sheet in which an easy-adhesion coat layer is provided on a surface to be bonded to a filler constituting the solar cell module, and the easy-adhesion coat layer has a cross-linked structure. It is set as the sheet | seat for solar cell backside sealing characterized by these.

  The invention according to claim 2 is the solar cell back surface sealing sheet according to claim 1, wherein the easy-adhesion coat layer is a water-dispersed ionomer type polyurethane resin.

  The invention according to claim 3 is the solar cell backside sealing sheet according to claim 1 or 2, characterized in that the softening point temperature of the film made of water-dispersed ionomer type polyurethane is 100 ° C or higher. It is.

  The invention according to claim 4 is a polyfunctional isocyanate-based compound, a polyfunctional epoxy-based compound, a melamine-based compound, (Chemical Formula 2) (where R1, R2, R3, and R4 are hydrogen, halogen, an alkyl group, an alkoxyl group, ( (Meth) acryloyl group, allyl group, vinyl group, glycidyl group, isocyanate group, mercapto group, group selected from any of substituents having an amine group) The solar cell back surface sealing sheet according to any one of claims 1 to 3.

  Chemical formula 2 is the above compound.

  Invention of Claim 5 is a coupling agent which has a glycidyl group, an amino group, and an isocyanate group in the component contained in an easily bonding coat layer, The solar cell back surface sealing of Claim 4 characterized by the above-mentioned. It is a sheet.

  The invention described in claim 6 is characterized in that the easy-adhesion coat layer is a mixture of a resin selected from "polyester resin or epoxy resin" and "acrylic resin", and the back surface of the solar cell according to claim 1 This is a sealing sheet.

  The invention according to claim 7 is characterized in that at least one of a resin selected from "polyester resin or epoxy resin" and "acrylic resin" can form a crosslinked structure. Alternatively, the solar cell back surface sealing sheet described in 5 is used.

  In the invention according to claim 8, the compound contained in the easy-adhesion coat layer is the above (Chemical Formula 1) (where R1, R2, R3, and R4 are hydrogen, halogen, alkyl group, alkoxyl group, (meth) acryloyl group, allyl group). A sheet selected from the group consisting of a vinyl group, a glycidyl group, an isocyanate group, a mercapto group and a substituent having an amine group). .

  Invention of Claim 9 is a coupling agent which has a glycidyl group, an amino group, and an isocyanate group for the component contained in an easily bonding coat layer, The solar cell back surface sealing for Claim 8 characterized by the above-mentioned It is a sheet.

The invention described in claim 10 is the solar cell back surface sealing sheet according to any one of claims 1 to 9, characterized in that an easy-adhesion coat layer is provided on a polyester base material.

  The invention according to claim 11 is a solar cell back surface sealing sheet according to any one of claims 1 to 10, characterized in that it has a multilayer structure including at least one polyester base material provided with an easy-adhesion coat layer. .

The invention according to claim 12 is characterized in that an inorganic compound vapor deposition layer is provided on at least one of the polyester base materials of all the base materials constituting the multilayer structure. It is a stop sheet.
It is what.

  Adhesiveness between solar cell backside sealing sheet made of polyester film such as polyethylene terephthalate, which has excellent electrical insulation, instead of aluminum foil, which causes short circuit by contact, and ethylene-vinyl acetate copolymer as filler It is possible to provide a sheet for sealing the back surface of a solar cell that does not decrease.

  Hereinafter, the present invention will be described in detail. The solar cell back surface sealing sheet according to the present invention is characterized in that the surface of the solar cell back surface sealing sheet that forms the solar cell module, particularly the surface to be bonded to the ethylene-vinyl acetate copolymer is “water-dispersed ionomer type”. A polyurethane resin, or a coating agent obtained by blending any of these with a polyfunctional isocyanate compound, a polyfunctional epoxy compound, a melamine compound, or a compound of (Chemical Formula 2) as a crosslinking agent, or “A coating agent in which a resin selected from a polyester resin or an epoxy resin and an acrylic resin, or a compound having a structure of (Chemical Formula 2) is further blended” is provided. However, in (Chemical Formula 2), R1, R2, R3, and R4 have hydrogen, halogen, alkyl group, alkoxyl group, (meth) acryloyl group, allyl group, vinyl group, glycidyl group, isocyanate group, mercapto group, and amine group. Selected from any of the substituents.

  The effect is particularly high when the component contained in the easy-adhesion coat layer is a coupling agent having a glycidyl group, an amino group, or an isocyanate group.

  The easy adhesion coat layer is designed in consideration of the adhesion to the solar cell back surface sealing sheet and the filler constituting the solar cell module, particularly the adhesion to the ethylene-vinyl acetate copolymer, In particular, the easy-adhesion coat layer needs to consider the adhesion to the ethylene-vinyl acetate copolymer from the above-described contents. Usually, an ethylene-vinyl acetate copolymer used as a filler for a solar cell module is one having a vinyl acetate content of 10 to 40% by weight to ensure the heat resistance and physical strength of the solar cell module. In addition, the ethylene-vinyl acetate copolymer is crosslinked by heat or light.

  When the ethylene-vinyl acetate copolymer is subjected to thermal crosslinking, an organic peroxide is usually used, and one that decomposes at a temperature of 70 ° C. or higher to generate radicals is used. Usually, those having a decomposition temperature of 50 ° C. or more with a half-life of 10 hours are used, and 2,5-dimethylhexane-2,5-dihydroxyperoxide, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, α, α '-Bis (t-butylperoxyisopropyl) benzene, n-butyl-4,4-bis- (t-butylperoxy) valerate, t-butylperoxybenzoate, benzoyl peroxide and the like are used.

  In the case of photocuring, a photosensitizer is used, and hydrogen abstraction type (bimolecular reaction type) such as benzophenone, methyl orthobenzoylbenzoate, 4-benzoyl-4′-methyldiphenyl sulfide, isopropylthioxanthone, etc. As the internal cleavage type initiator, α-hydroxyalkylphenone type such as benzoin ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl, etc. Phenyl ketone, alkylphenyl glyoxylate, diethoxyacetophenone and the like can be used. Further, as α-aminoalkylphenone type, 2-methyl-1- [4 (methylthio) phenyl] -2-morpholinopropane-1, 2-benzyl-2-dimethylamino-1- (4-morpholino) Phenyl) -butanone-1 and the like, and acylphosphine oxide and the like are also used.

  A silane coupling agent is also blended in consideration of adhesion to the glass plate constituting the solar cell module, and vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, Vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane , Γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, and the like.

  Furthermore, an epoxy group-containing compound may be blended for the purpose of promoting adhesion and curing. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, acrylic glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester , Glycidyl methacrylate, butyl glycidyl ether and other compounds, oligomers containing an epoxy group with a molecular weight of several hundred to several thousand, and polymers with a weight average molecular weight of several thousand to several hundred thousand. Some cases are there.

  In addition, an acryloxy group, methacryloxy group or allyl group-containing compound is added for the purpose of improving the crosslinking, adhesiveness, mechanical strength, heat resistance, moist heat resistance, weather resistance, etc. of the filler, and (meth) acrylic Acid derivatives such as their alkyl esters and amides are most common. In this case, as the alkyl group, in addition to an alkyl group such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, A 3-chloro-2-hydroxypropyl group and the like can be mentioned. Further, esters of (meth) acrylic acid and polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, pentaerythritol and the like are also used. A typical amide is acrylamide. Further, as the allyl group-containing compound, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, diallyl maleate and the like are blended.

Furthermore, an inorganic compound for imparting flame retardancy, an ultraviolet absorber for imparting weather resistance, and an antioxidant for preventing oxidative degradation are variously blended. That is, it can be mentioned that the ethylene-vinyl acetate copolymer constituting the solar cell module is a resin composition in which various additives are blended in order to satisfy the functions required for the solar cell module. In other words, in order to consider the adhesiveness between the solar cell backside sealing sheet and the filler constituting the solar cell module, the resin composition is not simply an adhesive with the ethylene-vinyl acetate copolymer, but various additives. It is necessary to have the recognition of adhesion to an object, and it is necessary to consider that the various additives described above have an advantage for adhesion and may have a disadvantage. Therefore, as a result of sincerity studies to improve the adhesion with the filler, ethylene-vinyl acetate copolymer, it was confirmed that the easy-adhesion coat layer described below is effective.

  As the easy-adhesion coat layer, first, “a water-dispersed ionomer type polyurethane resin, or a polyfunctional isocyanate compound, a polyfunctional epoxy compound, a melamine compound, a compound having a structure of Or a coating agent containing a mixture thereof.

  Water-dispersed ionomer-type polyurethane resins include “polyester polyols” obtained using polybasic acids or their ester-forming derivatives and polyols or their ester-forming derivatives, “acrylic polyols” having a hydroxyl group at the terminal / side chain, polyethylene "Polyether polyols" such as glycol and polypropylene glycol, as chain extenders, tolylene diisocyanate, xylylene diisocyanate or its hydrogenated product, hexamethylene diisocyanate, 4-4 'diphenylmethane diisocyanate or its hydrogenated product, isophorone diisocyanate Obtained by reacting these diisocyanates with adducts obtained by reacting these diisocyanates with polyhydric alcohols such as trimethylolpropane and water. In the structure of polyurethane resins obtained by the action of polyisocyanates such as the isurelet body or the isocyanurate body that is a trimer, a hydroxyl group, an amino group, or a sulfonic acid is used to improve water dispersibility. It has a structure obtained by copolymerizing a compound having a hydrophilic functional group such as a group, a carboxylic acid group, or a salt thereof. These hydrophilic functional groups not only give dispersion stability as an emulsion, but also improve adhesion to various substrates, especially polyester substrates, compared to solvent-soluble polyurethane resins. In terms of adhesion to the substrate, carboxylic acid groups, sulfonic acid groups, or salts thereof are particularly preferable.

  The softening point temperature of the film made of this water-dispersed ionomer type polyurethane resin is preferably a polyurethane resin having a heat resistance of 100 ° C. or higher. As described above, in the water-dispersed ionomer type polyurethane resin, a sulfonic acid group, a carboxylic acid group, or a salt thereof is introduced into the structure, and adhesion to various substrates can be improved. However, the point of improved adhesion to various substrates over solvent-soluble polyurethane resins is the improvement of hydrogen bonding and ionic bonding of sulfonic acid groups, carboxylic acid groups, or salts thereof with the substrate surface. There is a problem that these bonds are weak against water. In other words, in order not to cause a decrease in adhesion even when stored in the environment of 85 ° C.-85% RH described above, the influence of the fluidity of the film in the above storage environment or the permeation of water accompanying storage under high humidity. It is necessary to design the molecular structure to prevent. That is, it is necessary to mention the heat resistance of the water-dispersed ionomer-type polyurethane resin. From such a viewpoint, the heat flow starting temperature of the water-dispersed ionomer-type polyurethane resin used in the present invention is 100 ° C. or higher, more preferably 150. It is preferable that it is a polyurethane resin having a heat resistance of at least 180 ° C, more preferably at least 180 ° C.

It is also preferable to add a crosslinking agent to the water-dispersed ionomer type polyurethane resin in terms of further improving heat resistance. Examples of such cross-linking agents include tolylene diisocyanate, xylylene diisocyanate or hydrogenated products thereof, hexamethylene diisocyanate, 4-4 ′ diphenylmethane diisocyanate or hydrogenated products thereof, diisocyanates such as isophorone diisocyanate, or these isocyanates. Polyisocyanates such as adducts reacted with polyhydric alcohols such as trimethylolpropane, burettes obtained by reacting with water, or isocyanurates that are trimers, or these polyisocyanates It is possible to use blocked polyisocyanates obtained by blocking with alcohols, lactams, oximes and the like. Furthermore, it is possible to use various crosslinking agents utilizing the hydrophilic group of the ionomer type polyurethane. For example, an epoxy compound, a melamine compound, or a compound having the structure described in (Chemical Formula 2) can be mentioned. Here, (Chemical Formula 2) is R1, R2, R3, R4 is hydrogen, halogen, alkyl group, alkoxyl group, (meth) acryloyl group, allyl group, vinyl group, glycidyl group, isocyanate group, mercapto group, amine group. It is selected from any of the substituents it has. For example, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxy Silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) ) -Γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, and other various silane coupling agents. In particular, these compounds of (Chemical Formula 2) are expected to work with various additives, for example, silane coupling materials, etc., which are blended in EVA for solar cell fillers. It is expected to improve the adhesion with a certain EVA. The amount of these crosslinking agents is 0.1 to 10 parts per 100 parts of the water-dispersed ionomer type polyurethane resin. When the amount is less than 0.1 part, it is difficult to obtain the effect of adding a crosslinking agent. On the other hand, if it exceeds 10 parts, the pot life as a coating agent is remarkably shortened depending on the type of the additive.

  Next, an effective easy-adhesion coat layer is “a coating agent obtained by further blending a resin selected from polyester resins or epoxy resins and an acrylic resin, or a compound having a structure of (Chemical Formula 2)”. Can be mentioned.

  Examples of acrylic resins include (meth) acrylic acid, alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, 2- Polymers based on alkyl (meth) acrylate monomers that are ethylhexyl and cyclohexyl groups are used, and (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (alkyl) Examples of the group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group), N-alkoxy (meta ) Acrylamide, N, N-dialkoxy (meth) acrylamide, (alkoxy groups include methoxy group, etoxy Group, butoxy group, isobutoxy group, etc.), amide group-containing monomers such as N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, etc. Hydroxyl group-containing monomers, glycidyl (meth) acrylate, glycidyl group-containing monomers such as allyl glycidyl ether, silane-containing monomers such as (meth) acryloxypropyltrimethoxysilane, (meth) acryloxypropyltriethoxylane, (meth) acrylic Examples include those obtained by copolymerization of an isocyanate group-containing monomer such as loxypropyl isocyanate. This type of acrylic resin preferably has heat resistance as in the case of the water-dispersed ionomer type polyurethane described above. From such a viewpoint, a resin having a high glass transition point from the molecular structure and a resin capable of forming a crosslinked structure are preferable. In terms of forming a crosslinked structure, it is possible to use either a self-crosslinking type that forms a crosslinked structure by reacting within a molecule or between molecules, or a type that forms a crosslinked structure by blending a crosslinking agent. . If necessary, vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itacone It is also possible to copolymerize monomers such as acid monoester, (meth) acrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate and butadiene.

  The polyester type is obtained by using a polybasic acid or an ester-forming derivative thereof and a polyol or an ester-forming derivative thereof. As the polybasic acid component, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2, Two or more acid components such as 6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, maleic acid, itaconic acid, and polyol component Ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, trimethylolpropane, pentaerythritol, xylene glycol, dimethylolpropane, poly (ethyleneoxy) ) Glycol, poly (tetramethylene oxide) glycol, oily, aqueous, obtained by using one or more polyol components containing carboxylic acid groups, sulfonic acid groups, amino groups or salts thereof. A water-dispersible copolyester is mentioned. In addition, a polyester resin having a crosslinked structure formed as in the case of an acrylic resin can be used, and a thermosetting polyester resin using a monomer having an unsaturated bond in the structure can also be used.

  Typical examples of the epoxy type include bisphenol A type epoxy resins and phenol novolac type epoxy resins, but various polyfunctional epoxy compounds such as the above glycidyl group-containing acrylic resins, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene Epoxy compounds in which glycols such as glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and the like and epichlorohydrin are allowed to act, glycerin, polyglycerin , An epoxy compound obtained by reacting polychlorinated alcohols such as trimethylolpropane, pentaerythritol and sorbitol with epichlorohydrin, Phthalic acid, oxalic acid, can also be used such as epoxy compound reacted with the dicarboxylic acid and epichlorohydrin, such as adipic acid. At this time, it is possible to use compounds having various carboxylic acid groups, amino groups, and oxazoline groups as the curing agent, and further, the (meth) acrylic acid-based polymer, (meth) acrylamide-based polymer, and unsaturated dicarboxylic acid described above. An acid-containing acrylic polymer may be used. On the other hand, as the phenol resin, either a resol type or a novolac type can be used, and if necessary, an amine or an epoxy curing agent can be used in combination.

  In this type of coating agent, “polyester resin or epoxy resin” is blended in order to improve the adhesion to the polyester substrate used for the solar cell back surface sealing sheet. On the other hand, “acrylic resin” is blended in order to improve adhesion to EVA as a solar cell filler. In this sense, a blend of these resins is necessary to improve the adhesion between the solar cell back surface sealing sheet and the solar cell filler. The mixing ratio of “polyester resin or epoxy resin” and “acrylic resin” can be set appropriately according to the characteristics of these resins. The copolymerized self-crosslinking type can stabilize (compatibilize) the blended state as a coating material, in particular, by blending the compound of (Chemical Formula 2) described above. Moreover, as mentioned above, the compounding of the compound of (Chemical Formula 2) is expected to improve the adhesion between the coating material and EVA as the filler. Furthermore, as with the “water-dispersed ionomer type polyurethane resin”, improving heat resistance is effective in improving adhesion in an environment of 85 ° C. to 85% RH, and is suitable for thermosetting polyester resins or thermosetting epoxy resins. It is preferable to blend an acrylic resin capable of forming a crosslinked structure and further blend the compound of (Chemical Formula 2) as necessary.

By providing such an easy adhesion coating layer, it is possible to improve the adhesion between the solar cell back surface sealing sheet and the solar cell module filler. Generally, a solar cell module is manufactured in a batch system using an apparatus called a laminator, and the method is as follows (FIG. 2).

Step 1 Set a glass plate, a filler, a cell, a filler, and a sheet for backside sealing on a heated top plate (approximately 120 to 160 ° C.) Step 2 Vacuum the chambers 1 and 2 Step 3 Chamber 1 Open to the atmosphere and attach a heat-resistant rubber sheet to the module Step 4 Melt the ethylene vinyl acetate copolymer as the filler with the heat / pressure, embed the cell, glass plate / cell / back surface sealing sheet This is the end of adhesion and crosslinking / solidification of the filler.

  At this time, the process 4 is classified into a case where a crosslinking reaction is performed in an oven provided on a separate line after lamination and a case where a crosslinking reaction is performed inside the laminator. The former is a type called standard cure, and the latter is a type called fast cure. Each type has advantages / disadvantages, but in the case of fast cure, the time to apply heat is shorter than standard cure, which may affect the adhesion of the solar cell back surface sealing sheet. It is possible to improve the adhesion failure due to the EVA type by using the easy adhesion coat.

  As the material for the solar cell back surface sealing sheet for providing these easy-adhesion coat layers, the above-mentioned fluorine-based resin can also be used, but since it has various problems, a polyolefin-based resin, a polyester-based resin, Polyamide resins, polycarbonate resins, polyarylate resins, and the like can be mentioned, but polyester resins, particularly biaxially stretched polyester resins, are preferred in view of heat resistance, strength properties, electrical insulation, and the like. The polyester resin is obtained by using a polybasic acid or an ester-forming derivative thereof and a polyol or an ester-forming derivative thereof. As the polybasic acid component, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2, Two or more acid components such as 6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, maleic acid, itaconic acid, and polyol component Ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, trimethylolpropane, pentaerythritol, xylene glycol, dimethylolpropane, poly (ethyleneoxy) De) glycol, poly (tetramethylene oxide) glycol, and polyester obtained by using one or more polyol components containing carboxylic acid groups, sulfonic acid groups, amino groups, or salts thereof. However, it is possible to use general-purpose polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

  When a biaxially stretched polyester base material such as polyethylene terephthalate is used as the material for the solar cell back surface sealing sheet, there is no particular limitation, but according to the required function required as the solar cell back surface sealing sheet. It is possible to select materials. For example, when there is a concern about the effect of shrinkage due to heat when manufacturing a solar cell module, a polyester base material having a heat shrinkage rate of 1% or less, preferably 0.5% or less by performing an annealing treatment is used. It is possible to use. When weather resistance is required, UV absorbers such as benzophenone, benzotriazole, and triazine, hindered phenol-based, phosphorus-based, sulfur-based, tocopherol-based antioxidants, hindered amine-based light stabilizers are also appropriately used. It is possible to mix.

Further, when there is a concern about hydrolysis of the polyester base in terms of weather resistance, the number average molecular weight is in the range of 18,000 to 40,000, and the cyclic oligomer content is 1.5 wt% or less,
It is preferable to use a polyester base material having an intrinsic viscosity of 0.5 wt% or less and an intrinsic viscosity of 0.5 dl / g or more. In addition, when the polyester molecule end is a carboxylic acid group, it acts as a heat, water, and acid catalyst and is most affected by hydrolysis, so the number average molecular weight is increased without increasing the amount of the terminal carboxylic acid. The terminal carboxylic acid group may be sealed with a carbodiimide compound, an epoxy compound, or an oxazoline compound. However, in terms of the above-described heat shrinkage rate and weather resistance, it is shown that the polyester base material can be selected according to the function required as a solar cell module although it seems to be repeated, and is limited to these. However, it is possible to use a very general polyester resin such as general-purpose polyethylene terephthalate as a base material. A schematic diagram at this time is shown in FIG.

  Although the polyester base material used for the solar cell backside sealing sheet may be transparent, it is preferable to use a white polyester film from the viewpoint of improving the power generation efficiency of the solar cell element. In particular, when the solar cell back surface sealing sheet has a multilayer structure, it is possible to provide a white polyester film on at least the base material bonded to the filler. From this content, the easy-adhesion coat layer described above may be provided on the white polyester film.

  The white polyester film used at this time is a “pigment dispersion type” in which white additives such as titanium oxide, silica, alumina, calcium carbonate, and barium sulfate are added, or polymers and fine particles that are incompatible with polyester are added, and biaxial It is possible to use a “fine foam type” or the like that is whitened by forming voids at the blend interface during stretching. In the “fine foaming type”, the polymer incompatible with the polyester is preferably a polyolefin resin such as polyethylene, polypropylene, polybutene, polymethylpentene. If necessary, polyalkylene glycol or a copolymer thereof can be used as a compatibilizing agent. Specific examples of the fine particles include organic particles and inorganic particles. Silicon particles, polyimide particles, crosslinked styrene-divinylbenzene copolymer particles, crosslinked polyester particles, fluorine-based particles, and the like are used. As the inorganic particles, calcium carbonate, silicon dioxide, barium sulfate or the like is used.

  In consideration of the gas barrier property described later, the solar cell back surface sealing sheet preferably has a multilayer structure having at least a white polyester base material provided with the above-described easy-adhesion coat layer as an essential component. Although various types of base materials can be used, polyester base materials such as polyethylene terephthalate are preferable. And it is preferable to use the gas-barrier base material which provided the inorganic compound vapor deposition layer for at least any one layer of the polyester base material which comprises the sheet | seat for solar cell backside sealing. Examples of the inorganic compound include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, indium oxide, and composite oxides thereof. Any inorganic compound may be used as long as it is transparent and has a gas barrier property such as oxygen and water vapor. Among them, aluminum oxide and silicon oxide are particularly preferable.

The optimum conditions of the thickness vary depending on the type and configuration of the inorganic oxide used, but generally the thickness is preferably in the range of 5 to 300 nm, and the value is appropriately selected. If the film thickness is less than 5 nm, a uniform film cannot be obtained, and the film thickness is not sufficient for exhibiting the barrier function. When the film thickness is larger than 300 nm, the film is subjected to flexibility, and there is a possibility that a crack is easily generated due to external stress. Preferably, it exists in the range of 10-150 nm. As a method of providing these vapor deposition layers, it can be formed by a normal vacuum vapor deposition method, but other thin film formation methods such as sputtering, ion plating, and plasma vapor deposition (CVD) are used. Is also possible. Further, if necessary, an overcoat layer composed of a part of ethylene-vinyl acetate copolymer or a completely saponified product and a silane compound is provided on the vapor deposition layer of the inorganic compound from the viewpoint of further improving the gas barrier property. It doesn't matter. These overcoat layers can be provided mainly by a technique such as gravure coating. A specific example of the solar cell back surface sealing sheet having this configuration is shown in FIG.

  The production method of the solar cell back surface sealing sheet is as follows. The easy-adhesion coat layer can be provided by various coating methods such as gravure coating, reverse coating, roll coating, die coating, etc., as a simple substance of the above-mentioned polymer or diluted with various solvents as necessary. You may pass through a drying process or a thermosetting process as needed. In addition, after the polyester resin is extruded in a molten state and cooled with a cooling roll, a film is formed, and then an easy-adhesion coat layer is provided. It is also possible to provide an adhesive coat layer.

  When the polyester base material provided with this easy-adhesion coat layer is further bonded to the gas barrier base material described above, it can be laminated using a known method such as dry lamination using a urethane-based adhesive or the like. is there.

  From the above contents, it is possible to obtain a solar cell backside sealing sheet having good adhesion to the ethylene-vinyl acetate copolymer resin composition that is a filler of the solar cell module.

Although the Example of this invention is shown below, it is not necessarily limited to this.
[Polyester substrate]
<Base material: 1>
A “micro-foaming type” white polyethylene terephthalate film having a thickness of 50 μm was used. This polyester film is a multilayer film of two types and three layers in which a fine foam layer is provided in the intermediate layer, and the intermediate layer occupies 80%. Corona treatment was performed on both sides of this white polyethylene terephthalate film. This substrate was used as a substrate to be bonded to the solar cell module filler.

<Substrate: 2>
A “pigment dispersion type” white polyethylene terephthalate film having a thickness of 50 μm was used. This polyester film uses titanium oxide as a white pigment. Corona treatment was performed on both sides of this white polyethylene terephthalate film. This substrate was used as a substrate to be bonded to the solar cell module filler.

<Base material: 3>
A normal biaxially stretched polyethylene terephthalate film having a thickness of 12 μm was provided with an alumina vapor deposition layer of 20 nm by PVD, and a coating layer made of a silane compound was provided as an overcoat layer on a completely saponified ethylene-vinyl acetate copolymer. This substrate was used as a gas barrier substrate.

<Substrate: 4>
A hydrolysis-resistant polyethylene terephthalate film having a thickness of 125 μm was used as the main substrate. The base material has an oligomer content of 0.5 wt%, a number average molecular weight of 19,500, and an intrinsic viscosity of 0.7 dl / g.

[Creation of solar cell back surface sealing sheet]
<Base material: 1> or <Base material: 2> is a urethane-based adhesive {polyester-based main agent + (isophorone diisocyanate / xylylene diisocyanate) so that the deposition layer of <base material: 3> is on the bonding surface side. Was laminated by a dry laminating method. This laminate was further laminated in the same manner as in <Substrate: 4>. The obtained laminate was aged for 96 hours in a 50 ° C. environment. The laminate thus obtained was used as a solar cell back surface sealing sheet.

[Create evaluation sample]
A fast cure type ethylene-vinyl acetate copolymer resin composition was used as a filler for a solar cell module. The solar cell used was polycrystalline silicon. A cell sandwiched between the ethylene-vinyl acetate copolymer sheets having the same size and a thickness of 600 μm was placed on an A4 size tempered glass, and a sheet for backside sealing described in the following examples was further provided thereon. After preheating at 40 ° C. for 3 minutes in advance, a laminate was applied at 150 ° C. under vacuum for 6 minutes and pressure bonding for 8 minutes under a pressure of 1 atm. This sample was used in the following evaluation.

[Evaluation methods]
Immediately after laminating the above sample and when the accelerated test was conducted for 250, 500, 750, 1000 hours in an environment of 85 ° C.-85% RH, the laminate strength (15 mm width) was measured with a tensilon at a crosshead speed of 300 mm / min. The test was accepted when the rate of change in strength before and after storage evaluation was 50% or more.

[Effect of easy-adhesion coat (water-dispersed ionomer type polyurethane resin system)]
<Example 1>
The solar cell back surface sealing sheet was prepared and evaluated without providing an easy-adhesion coat layer on <Substrate: 1>. The results are shown in Table 1.

<Example 2>
The same procedure as in Example 1 except that <Substrate: 1> was previously provided with a water-dispersed ionomer type polyurethane resin (manufactured by Dainippon Ink) having a softening point temperature of 180 ° C.

<Example 3>
The same procedure as in Example 1 was performed except that a water-dispersed ionomer type polyurethane (manufactured by Dainippon Ink) having a softening point temperature of 95 ° C. was previously provided on <Substrate: 1>.

<Example 4>
<Substrate: 1> In advance, 100 parts of water-dispersed ionomer type polyurethane resin (Dainippon Ink) with a softening point temperature of 180 ° C. is added to β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (Azmax). Example 1 is the same as Example 1 except that an easy-adhesion coat layer containing 10 parts is provided.

<Example 5>
5 parts of HDI polyisocyanate for aqueous urethane (Dainippon Ink) was blended with 100 parts of water-dispersed ionomer type polyurethane resin (Dainippon Ink) with a softening point temperature of 180 ° C. in advance in <Substrate: 1>. The same as Example 1 except that an easy-adhesion coat layer was provided.

[Effect of easy-adhesion coat (acrylic resin system having a crosslinked structure)]
<Example 6>
The same as Example 1 except that a thermosetting epoxy melamine coating agent (Dainippon Ink) was provided on <Substrate: 1>.

<Example 7>
The same as Example 1, except that <Substrate: 1> was provided with a silane-modified acrylic resin-based coating agent (Arakawa Chemical).

<Example 8>
The same as Example 1, except that <Substrate: 1> was provided with a coating agent containing 40% by weight of the coating agent described in <Example 6> and 60% by weight of the coating agent described in <Example 7>.

<Example 9>
Example except that the coating agent of <Example 8> was further provided with an easy-adhesion coat layer containing 10 parts of β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (manufactured by Azmax) for 100 parts. Same as 1.

<Example 10>
<Base material: 2> Implemented except using a polyester base material (manufactured by Teijin DuPont) coated in-line at the time of polyester film formation with a coating agent containing water-dispersed self-crosslinking acrylic + water-dispersed copolymer polyester Same as Example 1.

<Example 11>
The same as Example 1 except that <base material: 2> was provided with water-dispersed uncrosslinked acrylic (manufactured by Johnson polymer) + water-dispersed copolymer polyester (manufactured by Toyobo).

[effect]
Compared to Example 1, the effect of the easy-adhesion coat is clear. In the case of a water-dispersed ionomer type polyurethane resin, the adhesiveness with the filler constituting the solar cell module at 85 ° C.-85% RH storage can be obtained by selecting the resin according to the softening point temperature of the film and adding a crosslinking agent. It is confirmed that it changes greatly. In the case of polyester resin or acrylic resin, as can be seen from Examples 6 and 7, each resin alone has poor adhesion to the filler constituting the solar cell module. It is confirmed that the adhesion is greatly improved by blending the above or blending additives. It is clear that even if a crosslinked structure is formed, this content is not effective for adhesion unless the coating material is compatible with both the polyester base material used for the solar cell back surface sealing sheet and EVA used for the solar cell module filler. . Moreover, although the coating agent which does not form a crosslinked structure like Example 11 is excellent in initial contact | adhesion, it can confirm that the fall of the adhesiveness in 85 degreeC-85% RH storage is remarkable. From the above contents, by using the solar cell back surface sealing sheet provided with the easy-adhesion coating agent of the present invention, it is possible to create a module that does not impair the quality of the solar cell.

It is a schematic diagram of a solar cell module. It is a schematic diagram of solar cell module creation. It is a schematic diagram of the sheet | seat for solar cell backside sealing which provided the easily bonding coat layer in the polyester base material. It is a schematic diagram of a solar cell back surface sealing sheet in which an easy-adhesion coat is provided on a white polyester base material layer and a gas barrier layer is further interposed.

Explanation of symbols

A: Solar cell module A-1: Solar cell A-2: Filler A-3: Glass plate B: Back surface sealing sheet B-1: Easy adhesion coat layer B-2: Polyester layer B-3: White polyester Layer B-4: Adhesive layer B-5: Inorganic compound vapor deposition layer B-6: Overcoat layer C: Laminator C-1: Top plate C-2: Chamber 1
C-3: Chamber 2
C-4: Rubber sheet

Claims (12)

  A solar cell back surface sealing sheet in which an easy adhesion coat layer is provided on a surface to be bonded to a filler constituting the solar cell module, wherein the easy adhesion coat layer has a cross-linking structure. Stop sheet.   The solar cell back surface sealing sheet according to claim 1, wherein the easy adhesion coating layer is a water-dispersed ionomer type polyurethane resin.   The solar cell back surface sealing sheet according to claim 1 or 2, wherein a softening point temperature of a film made of water-dispersed ionomer-type polyurethane is 100 ° C or higher. Polyfunctional isocyanate compounds, polyfunctional epoxy compounds, melamine compounds,

(However, R1, R2, R3, and R4 are any of hydrogen, halogen, alkyl group, alkoxyl group, (meth) acryloyl group, allyl group, vinyl group, glycidyl group, isocyanate group, mercapto group, and amine-containing substituent. 4. The solar cell back surface sealing sheet according to claim 1, wherein any one of the groups selected from the above is included in the easy adhesion coat layer. 5.   The solar cell back surface sealing sheet according to claim 4, wherein the component contained in the easy-adhesion coat layer is a coupling agent having a glycidyl group, an amino group, or an isocyanate group.   The solar cell back surface sealing sheet according to claim 1, wherein the easy-adhesion coat layer is a mixture of a resin selected from "polyester resin or epoxy resin" and "acrylic resin".   6. The solar cell back surface sealing according to claim 1, wherein at least one of a resin selected from “polyester resin or epoxy resin” and “acrylic resin” can form a crosslinked structure. 7. Stop sheet.   The compound contained in the easy-adhesion coat layer is the above (Chemical Formula 1) (where R1, R2, R3 and R4 are hydrogen, halogen, alkyl group, alkoxyl group, (meth) acryloyl group, allyl group, vinyl group, glycidyl group, isocyanate) The solar cell back surface sealing sheet according to claim 6 or 7, wherein the sheet is a group selected from any of a group, a mercapto group and a substituent having an amine group.   The solar cell back surface sealing sheet according to claim 8, wherein the component contained in the easy-adhesion coat layer is a coupling agent having a glycidyl group, an amino group, or an isocyanate group.   The solar cell back surface sealing sheet according to any one of claims 1 to 9, wherein an easy-adhesion coat layer is provided on a polyester base material.   11. The solar cell back surface sealing sheet according to claim 1, comprising a multilayer structure including at least one polyester base material provided with an easy adhesion coating layer. The solar cell backside sealing sheet according to any one of claims 1 to 11, wherein an inorganic compound vapor deposition layer is provided on at least one of the polyester base materials of all the base materials constituting the multilayer structure.

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